[Sleepy1]

I wanted to share my successful transaxle swap with a 4.310 final drive ratio to a 3.722 ratio (14% Taller) in my 2005 Scion XB.

(Pics Attached in Following Posts)

Overall Impressions:
I am very happy with the conversion and see a reduction of 500rpm at 70mph. The original gearing was 3500rpm at 70mph, but is now at 3000rpm. Additionally the new 4th gear is at 3575rpms at 70mph. In essence, it feels like I’ve gained another gear. Acceleration from 1st feels much more usable since I am not shifting into 2nd halfway through an intersection. I have not calculated my difference in MPG yet. I am still on my first tank since the conversion.

Findings / Data:
The Gen I Scion XB has a Toyota C5X series transaxle that is different than the Toyota Echo’s C150. The XB’x C5X uses the larger/stronger gears like the Toyota Corolla with the 8-bolt differential. This would allow for someone to install a stock or aftermarket limited slip differential as an option. For my conversion I used a 1993 Toyota Corolla C52 Transaxle originally mated to the 1.6l 4A-FE motor. Please note that the more powerful 1.8l 7A-FE Corolla gearing is different.

2005 Scion XB Gear Ratios:
1st 3.545, 2nd 1.904, 3rd 1.310, 4th 0.969, 5th 0.815 with 4.310 Final Drive

1993-1997 North America Toyota Corolla with 1.6l 4A-FE:
1st 3.545, 2nd 1.904, 3rd 1.310, 4th 0.969, 5th 0.815 with 3.722 Final Drive

Scion Vehicle Speed Sensor (VSS)
The Scion does not use a mechanical or digital VSS in the transaxle. Where a VSS would be located is blocked off with a plug. Speed is determined by the ABS.

Scion Shift Housing
The Shift Housing on the XB is different from earlier C5X series transaxles. While they look similar there are key differences. The housing cover is machined slightly different and cannot be swapped between versions, the shift rod is the same diameter / length and CAN be swapped if some of the teeth are ground off/removed to account for the ‘fingers’ and alignment mechanism. Additionally, the orientation of the shifter housing is the same as the Toyota Corolla. The Yaris and MR2 use a different orientation.

Scion XB Transaxle Mounting Points
The Scion uses mounting points similar to the Toyota Echo and earlier Tercels/Paseos. This makes the case of the Scion’s C5X transaxle unique and necessitates drilling / tapping 3 holes if using another C5X case. The factory bolts are M10 x 1.25.

My Approach:
For my conversion, I located a 1993 Corolla with a 1.6l 4A-FE at the local Pick-N-Pull autoparts yard. For $99, I was able to purchase and remove the entire transaxle. This was far cheaper than what many online companies are charging for new 3.722 gear sets. My plan was to use the Scion XB bell-housing, brackets, and shift housing innards with the Corolla Case/Gears.

The Corolla is a good swap candidate for several key reasons. There is a large selection of good transmissions to choose from at a Pick-N-Pull for cheap. I wanted to use the stock size 8-bolt differential that is stronger with good aftermarket parts availability. The shifter housing orientation is the same as the Scion XB. Most Corollas are not raced or modified, so finding a transmission that wasn’t abused isn’t hard. The Scion XB is only 110pounds more than the corolla and has more hp/torque. Lastly, I could always swap in the 0.725 5th gear from a 99-02 Corolla with the C59 transmission. This would further reduce my RPMs by 400 and make the overall transaxle gearing Taller than the 3.526 final drive with a 0.815 5th from the Toyota Echo. (I haven’t done this modification, but it is common within the MR2 forums.)

Bell Housing Swap:
There are several forum articles detailing the steps needed to swap bell housings on Toyota transaxles. For my conversion, I measured the Corolla’s differential rotation to set a baseline using an inch/pound torque wrench. Unfortunately, I do not have pictures, but I fabricated an insert that would spin the differential through the CV axle hole. I took an old 5/8in 6-point socket and trimmed off 4 points. This allowed the socket to reach down and rotate the differential using the spider-gear link pin. Referencing several articles on Toyota bell-housing swaps, I removed the bearing-race and shim from the Corolla bell housing and reinstalled it in the Scion XB bell housing. Once I bolted the Corolla transaxle together with the Scion XB bell housing, I measured the differential again and found the torque measurement to be the same and within spec. Once complete, I installed new CV axle seals from the local parts store chain.

Shift Housing Shaft Swap:
Since the housing cover and innards were not compatible between transmission Scion XB / Corolla cases, and the shift rod orientation where the shifter cable attaches is different, I swapped out the housing shaft and used the rest of the Corolla components. To complete this, I had to grind off 1 tooth from the shift rod to allow the Corolla components to fit. I reused all the Scion XB shifter cables and brackets.

Drilling / Tapping Corolla transaxle to install drivers-side mount:
The mounting of the Scion XB mount is very similar to the Tercel/Paseo. Fortunately, installing the Corolla transaxle in a Tercel is a very well documented procedure on one of the Tercel forums. The Corolla transaxle has the appropriate mounting boss and case reinforcements to support these holes, but they are not machined from the factory. For my install I mounted the transaxle onto an engine stand and used a cordless drill. Once drilled, I tapped the holes and installed the mount.

Alternative:
You could always just have a shop swap out the 3.722 final drive into your stock Scion XB case. (If you can find a shop willing to do this.) However, the costs to tear down and properly assemble the transmission are much-much more than my $99 dollar investment.

Conclusion:
I hope this article was interesting to those that would consider this swap. For me, this swap was very worthwhile and I bought my Scion XB with a worn clutch knowing I wanted to figure out a way to complete a gearing swap. While this is more complex than a bolt-in swap, I was able to complete this over a weekend at home. Please note, I am a car enthusiast and not a professional mechanic. This write-up was for informational purposes only. Modifying my cars at home in my garage is my passion and not my profession.